A variety of resources are available for allocation in a modern wireless communications system. For example, in the so-called CDMA2000 standard, the RC3 common air interface has been defined to specifically facilitate voice communications and the RC4 common air interface has been defined to specifically facilitate data communications. These two resources are usually allocated, as indicated, based upon the type of communication being serviced (i.e., voice or data)
Unfortunately, allocation decisions with respect to these two common air interface types can lead to an inefficient allocation of other attendant resources of the system. For example, a given system of this type will have a finite number of orthogonal variable spreading factor codes (such as, for example, Walsh codes) and a given number of radio frequency (RF) resources (such as base site RF interference resources) to use when supporting communications.
In general, for various reasons, a communication system of this type is Walsh code limited; that is, the total number of available Walsh codes (such as, for example, about 60) can usually only support a lesser number of RC3-type voice communications (as one example, the need to accommodate both so-called soft and softer handoffs will usually increase the number of Walsh codes that are dedicated at any given instant to support a single call). Conversely, an RC4-type data call will usually only consume approximately one half as many Walsh codes per call as an RC3-type voice call.
Therefore, in general, the more a system allocates RC3 common air interface types, the smaller the corresponding pool of available Walsh codes. At the same time as the number of Walsh codes diminishes to support a given number of RC3-type calls, however, there can remain a relatively larger number of radio frequency resources. That is, though a given system cell may be unable to support one additional incremental RC3-type call due to an inadequate available supply of Walsh codes, that cell may nevertheless still have available radio frequency resources that could otherwise be allocated to support communications but for the Walsh code limitations.
A somewhat similar situation exists for RC4-type data communications. In general, RC4-type calls tend to require more radio frequency resources per call than do RC3-type calls. Therefore, a large number of RC4-type calls in a given cell will tend to use up the radio frequency resources while leaving an available pool of Walsh codes.
To date, prior art approaches tend to associate a given service (such as data, telephony, dispatch, and so forth) with a given corresponding common air interface. Other supporting resources, such as Walsh codes and radio frequency resources, are then provided in numbers that meet whatever design criteria might be established by the system designer. This tends, unfortunately, to lead to systems having too few or too many such resources during at least some modes of operation. One prior suggestion posits that so-called quasi-orthogonal variable spreading factor codes can be used when a given cell has run out of orthogonal codes. Unfortunately, introducing less than wholly orthogonal codes will likely lead to sub-optimum performance under many operating conditions.
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